diff --git a/report.tex b/report.tex
index 48f036c..eae8b98 100644
--- a/report.tex
+++ b/report.tex
@@ -260,7 +260,7 @@
     we can introduce $\pi := \Partial{t} \phi$ and $\tensor{\psi}{_i} := \Partial{_i} \phi$, and rewrite the wave equation as
     \begin{equation}
       \begin{cases}
-        \pdvt{\phi} = \pi, \\
+        \Partial{t}{\phi} = \pi, \\
         \pdvt{\psi} = \pdv{\pi}{x}, \\
         \pdvt{\pi} = \pdv{\psi}{x}.
       \end{cases}